Endurance Water - Sports drink, bar or gel: which supplement is best during training?

Nutritional supplements are taken orally and are widely used by athletes to enhance performance and recovery. The supplements for sport purposes can be classified into dietary supplements, sport nutrition and ergogenic aids. Dietary supplements consist mainly of micronutrients but can also contain macronutrients and are believed to not enhance performance without a nutrient deficiency. Sport nutrition is mainly macronutrients such as carbohydrates and protein. Products categorised as sport nutrition are sport drinks, recovery drinks, energy drinks and protein bars among others. Ergogenic supplements contain products with a performance enhancing claim such as caffeine, creatine and beta-alanine (Wardenaar et al., 2017). The prevalence of nutritional supplementation is higher among elite athletes compared to their non-elite counterpart. With regards to sex prevalence of nutritional supplement, intake is similar (Knapik et al., 2016). Overall supplement use is the highest among endurance athletes compared to any other category of athletes (Garthe & Maughan, 2018).

As previously mentioned, carbohydrates are an important energy source for athletes. Therefore, carbohydrate supplementation improves endurance performance and maintains blood glucose levels during exercise (Campbell et al., 2008; Pfeiffer et al., 2010). Supplementation of carbohydrates can come in difference forms, such as sport drinks, gels and bars. It remains disputable whether there is a difference in effect on exercise performance between these administration forms (Guillochon & Rowlands, 2017). The three different sports supplements will be elaborated upon below.

Sports drinks are carbohydrates and sodium containing beverages. There are several practical advantages to a sports drink. For instance, sport drinks are the perfect way for athletes to hydrate themselves. Furthermore, athletes can regulate their fluid intake and decide for themselves how much water and carbohydrates they would like to ingest. A sports drink is a useful way to ingest more carbohydrates without feeling too saturated. In contrast, a sports drink can be inconvenient when travelling or exercising due to its weight (Atletiekunie, 2020). Sports drinks can also be bought in powder form to reduce the costs or to make travelling with the product more convenient. Another advantage of a powder is its longer shelf-life (Sebastiaan Horn, 2018).

Sport gels are designed to be consumed during exercise, instead of an energy bar. They are compact, energy dense and easy to use. The package of the gels can easily be opened by tearing off the edge of the gel or by opening the cap of the gel (Atletiekunie, 2020). The goal of most gels is to have maximum carbohydrate absorption, while ensuring minimal GI issues. In order to create maximal carbohydrate absorption, the effect of the gel on gastric emptying needs to be considered. Delayed gastric emptying influences the carbohydrate metabolism negatively through poor delivery of carbohydrate in the small intestine (Vist & Maughan, 1995). To minimise the delay in gastric emptying, osmolarity of the gastric contents and the effect the gels will have on them needs to be considered during the development of a during exercise supplement. 

Sports bars are energy dense bars containing high amounts of carbohydrates and varying amounts of protein, fat, fibre and other nutrients. These ingredients, besides carbohydrates, slow down the rate of gastric emptying and the absorption of carbohydrates (Jeukendrup & Gleeson, 2018). An advantage of sports bars compared to gels and drinks, is that they are more saturating. A randomised cross-over trial in twelve male cyclists, mountain bikers and triathletes, found that ingestion of a bar reduced peak performance when compared to a gel. Furthermore, the rate of perceived exertion (RPE), muscle tiredness and GI discomfort was increased when compared to a drink, gel or mixed carbohydrate format. Also, nausea and stomach fullness with a bar was higher relative to a gel and a drink. There was no difference in performance between these administration forms, but the mean peak power was the highest with a gel and the lowest with a bar (Guillochon & Rowlands 2017).

All the administration forms mentioned above have their advantages and disadvantages. When comparing the sports drinks and gels, which are commonly taken during exercise, studies did not find a difference in carbohydrate oxidation rate. A mixture of glucose and fructose administered either via a gel or a drink led to similar oxidation rates and oxidation efficiencies (Pfeiffer et al., 2010). Furthermore, in runners and triathletes, no statistically significant differences were reported in race finishing time between carbohydrate drinks or gels (Lee et al., 2014; Sareban et al., 2016), although gut comfort was decreased with the gel compared to a drink during triathlon (Sareban et al., 2016).

Although carbohydrate intake has a positive effect on exercise performance, the intake of carbohydrates is also associated with symptoms of GI distress. The presence of GI disfunction is backed-up with multiple laboratory studies that found a correlation between GI problems and large amounts of carbohydrate ingestion (O’Brien et al., 2013; Rowlands et al., 2012; Triplett et al., 2010). It was found that this occurrence is due to delayed gastric emptying by a high carbohydrate concentration and osmolarity (E. P. de Oliveira & Burini, 2014). For instance, a study found that consumption of carbohydrate-containing sports drinks during an 18 km run led to a higher incidence of GI complaints compared to plain water (Van Nieuwenhoven et al., 2000). This finding is also supported by the study of Zhang, O’Kennedy, and Morton (2015), who studied the composition of several energy gels on the market (Zhang et al., 2015). They concluded that the higher the energy density of the gels, the stickier the composition was, which induced GI issues during exercise. GI issues especially occurred in the absence of fluid intake when taking a gel. Another study of Pfeiffer et al. (2010), reported that 10-20% of runners, who consumed a carbohydrate gel during exercise, experienced GI issues during a 16 km run. However, no biological markers of GI disfunction were found in these athletes. Besides this, the study of Pfeiffer et al. (2009) found that GI problems mainly occurred in athletes with a history of GI complaints. The severity of the GI distress was associated with the severity of GI problems they experienced before.

CONCLUDING FINDINGS 
• There is no difference in carbohydrate oxidation rates between a drink and a gel and both administration forms have the same prevalence of GI issues. 
• A sports bar as administration form reduces peak performance and increases RPE, muscle tiredness and GI discomfort compared to a drink or gel.